Evaluation of fatigue performance of cement-treated composites based on residual strength through discrete element method

Fatigue damage is the process of material fatigue failure caused by cyclic loading, and the development of damage degrades the material properties. This paper aims to investigate the fatigue degradation law of cementtreated base (CTB) materials using a discrete element method (DEM) simulation technique. A fatigue evolution model was adopted to characterize the time-dependent fatigue damage under cyclic loading. Virtual semicircular bending (SCB) fatigue and residual strength tests at different fatigue stages were performed on mesoscale DEM model to evaluate the fatigue damage of CTB material. With residual strength variable, the fatigue damage model was established to reveal the accumulation of damage. The results show that the residual strength evolution nearly appears an exponential correlation with the fatigue stages. In the first stage, the strength degradation is stable and appears as approximately linear. At about 80% of the fatigue life, the degradation rate is significantly accelerated. The residual strength degradation rate is related to the initial stress level and decreases with the increase of stress ratio. At the same fatigue life stage, the greater residual strength attenuation will be generated with a lower load level. The fatigue damage evolution model indicates the fatigue damage accumulation approximately linearly in the early stage and rapidly in the late stage. The late fatigue stage has the main contribution to fatigue failure. The degradation law demonstrates the lower the load level is, the more the damage accumulation at the same fatigue life stage will be, and the corresponding critical damage is greater. Moreover, based on the strength degradation law, a prediction model is established to evaluate the residual fatigue life of pavement base material.